The invention pertains to digital data processing and, more particularly, to methods and apparatus for improving the processing power, ruggedness and/or longevity of digital data processing systems. The invention has application, by way of non-limiting example, in high-density embedded computer systems for image and signal processing applications such as radar, sonar, medical data acquisition and imaging, semiconductor device inspection and imaging, to name a few.
As processor speeds and circuit board densities increase, heat has become the limiting factor in computer design. Unless adequately dissipated, it can cause computers to run unpredictably or to crash. Excessive heat also substantially reduces component lifetimes. While this is merely annoying to the typical home or business user, it can prove catastrophic in mission critical applications, such as medical imaging, surveillance, and so forth.
The power requirements of reasonably sized individual computer circuit boards appear to be reaching asymptotic limits. Not so of the computers that house them. Manufacturers of at least high-end computer systems are pressured to include ever more circuitry in ever smaller chassis in order to meet customer throughput, redundancy and space requirements. The latter presents a real conundrum, however, since higher density board stacking reduces throughput and reliability, necessitating still more boards.
While cooling computer systemsxe2x80x94and, particularly, for example, high density systems which now consume up to 3000 watts per cubic footxe2x80x94can be accomplished using low temperature fluids or special gasses, forced air-convection cooling remains the preferred mechanism. The dilemma of using this choice is compounded where inlet operating temperature requirements for some systems, for example, high-density embedded systems, is typically 50xc2x0-55xc2x0 C., extending up to 70xc2x0 C. in some cases.
Holding junction temperatures to acceptable levels for meeting the required reliability with these high inlet temperatures is at best difficult, and at worst impossible, using prior art techniques. This is likewise true of maintaining basic component operation temperatures of 85xc2x0-100xc2x0 C. Moreover, many of these systems are placed in close proximity to people, so the noise-levels must typically be at or below 65-68 dB(A) at 1 meter.
An object of this invention is to provide improved methods and apparatus for digital data processing.
A more particular object is to provide such methods and apparatus as improve the capacity, density, efficiency, ruggedness, and/or longevity of such digital data processing systems.
Another object of the invention is to provide such methods and apparatus as can be used with air-cooling and more particularly, for example, forced air-coolingxe2x80x94as well as with other heat dissipation techniques.
Still other objects of the invention are to provide such methods and apparatus as can be implemented at low cost using existing components, materials and/or fabrication techniques.
The foregoing objects are among those attained by the invention which provides, in one aspect, a circuit board assembly comprising a substrate with one or more circuit components mounted thereon. A cover or other member is disposed adjacent to the substrate and, for example, spaced therefrom so as to define a plenum. One or more heat sinks (or other heat dissipative elements) are spring-mounted (or otherwise resiliently mounted) to the cover and, thereby, placed in thermal contact with one or more of the circuit components.
The heat sinks are self-aligning, according to related aspects of the invention. Thus, they are disposed on the cover so that when it is coupled to the substrate (permanently, removably or otherwise) the heat sinks come into thermal contact with the respective circuit components. According to further related aspects of the invention, the cover is a substantially planar member, such as, for example, a cold plate or other thermal conductor, that is sized to match the footprint of the substrate.
Further aspects of the invention provide a circuit board or circuit board assembly of the type used, for example, with other circuit boards in a computer or other equipment chassis. A circuit board according to this aspect of the invention includes one or more flow-diverting elements that define, at least in part, the board""s impedance to air flow in the chassis. The flow-diverting elements are adapted so that the overall impedance of the board substantially matches that of one or more of the other circuit boards.
According to related aspects of the invention, one or more of the flow-diverting elements are adapted to shape an air flow pattern within a plenum, for example, of the type established between the circuit board and its cover. Moreover, the flow-diverters can serve as heat sinks mounted, for example, to the substrate, the circuit components or (as discussed above) to the circuit board cover.
Still further aspects of the invention provide a circuit board assembly, e.g., of the types discussed above, in which cover is a substantially planar member with one or more structural elements that regulate shock and/or vibration in the cover and the circuit board. The structural elements may be rod-like or other elongate members, e.g., affixed to or incorporated into the planar member. Moreover, the structural members may be elongated heat sinks (or heat sinks of other shapes) that are coupled to the cover by spring-mounts, other resilient elements or otherwise.
In related aspects of the invention, the structural elements of the cover of a circuit board assembly as described above are adapted to control thermal and/or electromagnetic emission control, as well as shock and vibration.
The invention provides, in yet other aspects, a circuit board for use in a chassis that has a plurality of board insertion slots. The board includes an air inlet edge through which cooling air flow is received and an air outlet edge through which the air flow exits. The edges fall, for example, at the ends of a plenum defined, e.g., between the circuit board substrate and a cover as described above. A connector arrangement provides electrical, mechanical and/or other operational coupling between the circuit board and the chassis regardless of whether the board is disposed in a slot on a first (e.g., upper) side of a source of cooling air for the chassis or on a second (e.g., lower) opposite side of that source.
According to related aspects of the invention, the connector arrangement includes first (e.g., upper) and second (e.g., lower) connectors. The first (e.g., upper) connector provides, for example, electrical coupling between the circuit board and the chassis when the circuit board is disposed in the slot on the first (e.g., upper) side of the source of cooling air. The second (e.g., lower) connector provides such coupling when the board is disposed in the second (e.g., lower) slot on the opposite side of that source.
Related aspects of the invention provide a digital data processor in a cabinet having, for example, a central air inlet and a chassis with board insertion slots disposed on opposite sides of that inlet. Circuit boards, as described above, disposed in the chassis have connector arrangements that provide operational coupling regardless of which slots the boards are inserted into.
Other aspects of the invention provide a circuit board having two parts, each with an air flow inlet edge through which cooling air flow is received and an air flow outlet edge through which the air flow exits. Each of these parts is disposed on opposing sides of a central source of cooling air for the circuit board. That source, according to related aspects of the invention, is an air inlet incorporated into a panel that provides any of mechanical protection and electromagnetic interference (EMI) protection when the circuit-board is operationally coupled in a slot in a chassis. The inlet can be disposed centrally on the panel (e.g., between the first (or upper) and second (or lower) board parts) and can be aligned with a corresponding air inlet on the chassis cover of a digital data processor into which the board is inserted.
Yet still other aspects of the invention provide an improved chassis of the type having slots for slidable insertion of circuit boards. Each slot, according to this aspect of the invention, has a first air flow aperture disposed adjacent to a first edge of an inserted circuit board and a second aperture adjacent to a second edge of the board. The first air aperture is an air flow source; the second is an air flow exit. These apertures can be disposed, for example, on opposite ends of plenum in the circuit board, e.g., whether defined by a cold plate on which the board substrate is mounted or by a cover to which the board is coupled.
According to related aspects of the invention, the aforementioned chassis includes a cabinet with an air flow inlet. It provides to the first air flow aperture of the slots cooling air flow drawn from an environment outside the cabinet. Air flow exiting the slots"" second air flow apertures, conversely, can be directed to that outside environment or to another region within the covered chassis.
Still further related aspects of the invention provide a chassis as described above in which the first and second apertures are sized so that the impedance to air flow to the circuit board inserted in the slot substantially matches that to one or more other boards in the chassis. Yet still further related aspects provide a card cage having card insertion slots as described above that is vacuum or dip brazed, or by alternate process yielding a cage of sufficient structural stiffness and air-flow/interference sealing.
The invention provides, in still further aspects, circuit boards and chassis as described above in which an air and/or electromagnetic interference (EMI) seal is provided between each circuit board and the chassis slot into which it is inserted.
Further aspects of the invention provide digital data processors, e.g., in closed chassis or cabinets having centrally disposed air inlet grills, with card cages as described above and with circuit boards and circuit board assemblies, also as described above, in those chassis. Such digital data processors, as well as the assemblies of which they are made, provide for improved capacity, density, efficiency, ruggedness, and/or longevity of components that provide digital data processing functions. They can be used with air-cooling and more particularly, for example, forced air-coolingxe2x80x94as well as with other heat dissipation techniques. Moreover, they can be implemented at low cost using existing components, materials and/or fabrication techniques.